1. Field of the Invention
The present invention relates to an endoscope system.
This application is based on Japanese Patent Application No. 2006-215409, the content of which is incorporated herein by reference.
2. Description of Related Art
A known technique for changing the wavelength characteristics of observation light or illumination light involves disposing an etalon, in which distances between a plurality of optical elements can be varied by driving means composed of a piezoelectric element, in at least one of an image-acquisition optical system and an illumination optical system provided at a tip of an endoscope system (see, for example, Publication of Japanese Patent No. 2802061).
Spectroscopic information of a living organism or the like can be obtained by employing the technique disclosed in Publication of Japanese Patent No. 2802061. In the etalon disclosed in this patent document, driving means composed of a piezoelectric element that varies the distances between two or more optical elements is provided between the optical elements.
Etalons change their transmission characteristics using an optical interference effect. Accordingly, it is necessary to control the spectral characteristics with high accuracy by precisely controlling the distance between adjacent optical elements while keeping the distance close to about the coherence length of the light or less. In this case, only supplying a driving signal that is determined in advance in accordance with the distance between the optical elements to the driving means composed of the piezoelectric element is not sufficient to control the spectral characteristics with high accuracy.
An insertion portion of an endoscope that is inserted in a body cavity has an extremely small diameter and generally has a length of about 1 m or more. In addition, transmission lines of the driving voltage for operating the driving means composed of the piezoelectric element, transmission lines of signals of an image-acquisition device, and the like are disposed close together. Therefore, it is necessary to control the spectral characteristics with high accuracy while suppressing the effects of noise due to these electrical signals.